RED DWARF was so replete with continuity errors that the writers had to eventually retcon it by saying that the viewer could rationalise it that the show actually depicts the characters in three very similar parallel universes: Seasons 1-2 in one universe, Seasons 3-6 in another and Seasons 7-8 in yet another (differentiated by the fact that Lister and Rimmer hail from the 21st century in the first two seasons, the 23rd in the next four and the 22nd in the last two). This also explains how Lister had his appendix out twice

BATTLESTAR GALACTICA's continuity errors are legion. My favourite one is the pretty big nine-episode arc the characters spent looking for the Tomb of Athena which would show them the way to Earth, and then completely forgot about it afterwards, to the point where the show's science advisor Kevin Grazier asked Ronald D. Moore to explain how the Tomb fitted in with Fake Earth and Real Earth in Season 4 and RDM's answer was, "Oh crap, I forgot about that."

The other one is that Cavil was so clever that he removed all knowledge of the Final Five from the other six models, but didn't remove the basic knowledge that there are twelve models (hence Six's dialogue in the pilot mini-series), which would have made considerably more sense. There's also the kid that Boomer rescues from Caprica who promptly vanishes the second they get back to Galactica.